OK, so the data is not as clear as the hockey stick graph shows. The authors still conclude: “Our model provides a similar reconstruction but has much wider standard errors, reflecting the weak signal and large uncertainty encountered in this setting.”

Lets step back though at look at climatology basics. … Climate is exactly the same with long periods of swinging around narrow ranges followed by sudden jumps to another semi-stable range (i.e. entering and leaving ice ages). We do not know what kind of change of input it would take to force the climate system into an extreme jump or exactly what that jump would look like, we just know that such jump will happen at some point if inputs are changed enough.

… Can it possibly be responsible for mankind to conduct an uncontrolled, irreversible experiment on the only planet we, our children and grandchildren and all the rest of know life inhabit? I think not and the paper reference in this post does not change my conclusion at all.

There are two levels of rebuttal to this.

First, this comment invokes the precautionary principle — the swiss army knife of doomsterism. Describe an extreme scenario, then conclude that we must devote massive resources to stop it. No analysis needed of its likelihood, probable impacts — or comparison of that scenario with other possible extreme scenarios. But we cannot fund massive programs against every shockwave. At the end are links to posts discussing this.

Second, this comment does not accurately described the current situation. There are many dynamics at work. Here are a few of them.

(1) The threat is not certain

(1a) Both data and models have been inadequately verified

Much of the case showing anthropogenic global warnings rests on the proxy studies (i.e., reconstructions of temperatures using proxies) and untested climate models. The results of the first has been shown by multiple statistical experts to be unreliable. The second have never even been verified (doing so would require a well-funded multidisciplinary team of 3rd party experts).

(1b) The role of CO2

The projected rise in CO2 will not (as you imply) cause substantial temperature increases by itself. That requires forcing, increases humidity. This mechanism is conjectural. For example, rising humidity will increase cloud formation, which will offset some (most?) of the “greenhouse effect” warming.

(1c) CO2 is not the only factor at work

Humanity is changing the climate in many ways — primarily changes in land use (e.g., causing the Kilimanjaro glaciers to melt) and emitting particulates (an atmospheric cooling agent, also causes glacier melting). The net effect of these is unknown, to a large degree because premature scientific conclusions have limited funding. So it’s not clear where resources should be submitted. To learn more about this, a good starting point are the papers of the eminent meteorologist Roger Pielke Sr (Wikipedia); he discusses these issues at his website.

(2) There are other powerful climate cycles at work

To mention just three.

The past 2 century long warming might result from poorly understood natural long cycle, being a rebound from the little ice age (LIA). Without reliable proxy studies, the geographic extent of the LIA remains disputed.

Most significant and only dimly understood, are the effect of solar cycles on our climate.

All of these are activity researched by scientists. The media black-out on their work does not invalidate it. You can find links to some of this research on the FM reference page Science & climate – studies & reports.